Rdio’s strategy for third-party apps is a bit different. Last year, Rdio vice president of engineering Todd Berman told us he’d like to see developers deploy their wares across Rdio, Spotify, and other services — the same way developers build for iOS, Android, and other platforms, except hopefully with more of a standard in place. That way, it wouldn’t matter whether you subscribed to Rdio, Spotify, or any other subscription service — you’d still have a wide choice in apps to apply to that music. However, Rdio either hasn’t been as aggressive in courting third-party app developers, they prefer Spotify’s larger subscriber base, or something else is going on.

Rdio’s API Gallery is still as sparse as it was when we conducted that interview over a year ago, with only eight apps listed. Luckily for Rdio subscribers who’d like to supercharge their listening experience with third-party apps, Rdio API engineer Devin Sevilla has been tracking Rdio apps here. Other than the ones that need to be compiled (and are therefore only for coders, really), he has located 50 web apps, eight iOS apps, and two Android apps that run on Rdio.

You can view the full list here, which should grow as he bookmarks more of them. Here are some highlights for the web (this list is not exhaustive); we’ll tackle the mobile Rdio apps later.

Do you have seven minutes to spare? Head on over to 7min.io for a quick workout, featuring music pulled from Rdio and super-simple instructions on what to do and when to do it, presented through a really nice design. It’s always the same music, but hey, this is supposed to be your new routine, right?

Big data is crazy! Behold ArtistSear.ch, which creates a slick artist page for just about any band you can think of in mere seconds, by pulling music, tourdates, videos, biographies, Twitter feeds, Facebook links, and other goodies from 7Digital, Last.fm, Rdio, SongKick, The Echo Nest (publisher of Evolver.fm), TopSpin, and YouTube. A thousand web designers just groaned in unison.

When some rappers write rhymes, they really write them. Aspiring emcees could do worse than to check out RhymeLine, a web app for writing rap rhymes that puts an online notepad right next to a virtual iPhone, which plays instrumental beat tracks from Rdio for you to freestyle over, documenting your progress as you go, until you have a completed rhyme sheet. The app is a bit finicky, but the concept is neat.

It’s easy to fall into a rut, listening to the same songs or artist radio stations. When you were younger, you had time to track down fresh stuff (okay, maybe I am projecting here), but these days, it’s almost always time to make the donuts. Enter Rdio New Releases By Genre, built with much of the same special sauce that’s in Every Noise At Once (from Glenn McDonald of The Echo Nest, publisher of Evolver.fm). People are complaining that Spotify got rid of new releases; perhaps they’d give Rdio a try purely on the basis of this amped-up discovery tool.

It’s already helping me — somehow, I had no idea Rdio had just added releases from Fuxa, Belle and Sebastien, White Denim, and TV on the Radio — and that’s all without even scrolling.

People used to defend their use of Napster and other P2P networks by saying they were just auditioning stuff to see what they wanted to buy on vinyl or another physical format. Over a decade later, people are gravitating towards the licensed music subscriptions that charge the same $10 per month that Napster apparently wanted to charge. VinylStore makes it easy to use Rdio to audition vinyl; simply sign in with Rdio (or Last.fm) and you’ll be presented with a nice interface for buying vinyl from your Favorite artists. (In our testing, all of them were on Amazon, which means whatever you buy will go in your Amazon MP3 account too.)

Cribbed from the way Apple TV can display what you’re listening to on a nice big television, Rdio Display does the same thing with your computer monitor (or television, if you connect it). This would be great at a party, so everybody can see what’s playing, but it might be nice also for when you’re listening to Rdio’s radio stations from across the room. Pair with Rmotely for best results.